Pressure in fluids

Transcripts - Pressure in fluids

1.
Pressure in fluidsLiquids and gases also exert pressure…..

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Pressure in liquids Pressure in liquids acts equally in ALL directions, as long as the liquid is not moving.

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Pressure in gases Gases also exert pressure on things around them. The atmosphere exerts about 100 000 Pa on your body! Like liquids, pressure in gases acts equally in all directions, so long as the gas is not moving.

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Magdeburg hemispheres Magdeburg hemispheres demonstrate air pressure very well. When the air is sucked out, the air pressure acting on the outside will keep the spheres stuck together.

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Pressure and depth Pressure in a liquid increases with depth. Think about a column of water. The force at the bottom of the column….. …….is equal to the weight of all the water above it.

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Calculating Pressure The volume of water (V) is equal to the area of its base (A) multiplied by the height of the height h column (h) V=Axh area A

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Calculating Pressure Force (F) The mass of the water can be calculated using the Volume and the density of the height h water: mass = A x h x r The force (F) is equal to the weight area A of the water multiplied by gravity (g): F=Axhxrxg

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Calculating Pressure Finally we know that pressure, (P) is equal to the force, (F) divided by the area, (A). Axhxrx Pressure (p) = g A The area of the column cancels out, leaving us with: p=hxrxg YOU NEED TO KNOW THIS!

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Calculating pressure We can use this equation for calculating pressure differences in other liquids and gases, as long as we know the density. Turn to page 168 in your text books for some example questions on pressure, (there is a worked example on page 167 to help you).